Generator sets (referred to hereinafter as “gen-sets”) are used in a variety of mobile and stationary applications to provide electrical power to, for example, worksites where utility power is unavailable (e.g. remote mining operations), and electrical devices during temporary power outages, portable operations, or power-charging. Gen-sets typically include a power source such as, for example, a diesel engine and a generator (e.g. an alternator) driven by the power source to produce electrical power. Gen-sets can be rated for different operating parameters such as, for example, different power types (i.e. AC power or DC power), output frequencies, output power levels, voltage, and/or current ranges, etc. The rated operating parameters of a particular gen-set generally correspond to relatively stable operations of the gen-set, and the operation of various components of the gen-set can be manipulated to control the current state of these operating parameters. For example, the field current of the alternator is typically positively correlated to the amount of complex power (i.e. real power and reactive power) produced by the generator. Further, in AC gen-sets, the speed of the engine is typically positively correlated to the frequency of the generated power.
One or more electrical devices are generally connected to draw power from the gen-set. As these devices are turned on, an electrical load is applied on the generator and is transferred to the engine in the form of a mechanical load. Because many components powered by alternating currents are rated for a particular frequency (e.g. 60 Hz in North America and 50 Hz in Europe), and can be damaged by fluctuations in the frequency of the provided power, it is desirable to keep the speed of the engine relatively constant. However, increases in electrical load on the generator may demand that the engine increase a torque output, and if these demands rise to a high level and/or occur within a relatively short time span, the engine may be caused to lug or stall. That is, the amount of power required from the engine to drive the generator, as demanded by the electrical load, may exceed an immediate output capability or a total output capability of the engine, thereby causing excessive engine speed droop. Stalling or lugging the engine may decrease the productivity and efficiency of the engine.
Further, regulatory and standards-setting agencies have placed restrictions on how much the actual frequency and voltage produced by a gen-set can depart from the expected output without causing damage to electrical devices rated for those expected voltages and frequencies. For example, a 10% frequency excursion from 60 Hz may be allowed, and a 20% voltage excursion from 120 V may be allowed. As a result, gen-sets must be carefully controlled to minimize fluctuations in the frequency of the generated power (i.e. maintain the speed of the engine within an acceptable range of frequencies), while generating voltages that fall within an acceptable range of voltages. Regulatory agencies are also placing increasing emphasis on reduced emissions from engines, including gen-set engines, which limit acceptable air-fuel ratios for these engines. Moreover, the number of electrically powered components in use today has increased, thus demanding a greater amount of power from an engine of a given size. These factors, among others, have complicated the control of gen-sets.
One way to control the operation of a gen-set is to include a control system within the gen-set. One example of a gen-set controller is disclosed in U.S. Pat. No. 6,555,929 (“the '929 patent”) issued to Eaton et al. on Apr. 29, 2003. Specifically, the '929 patent discloses a gen-set controller that includes a method for preventing excessive reaction by a gen-set to a change in load. The gen-set controller is configured to communicate with a voltage regulator and any engine control modules (ECMs) included in an engine of the gen-set to control the output voltage and frequency of the gen-set. More specifically, the gen-set controller receives analog voltage and current outputs from the alternator, converts them to corresponding digital signals, and uses them to monitor the performance of the gen-set. The gen-set controller also uses these signals to calculate other gen-set operating parameters, such as output power, power factor, and alternator duty level and frequency, and provides command signals to the voltage regulator to control the voltage, current, and power output levels of the alternator. The gen-set controller further monitors information gathered by the ECM about the engine's operation, and provides control commands to the ECM to shutdown the engine, should a system fault occur. The gen-set controller monitors an output voltage and current of the gen-set during a first period of time and uses them to calculate a first average power output of the gen-set. Similarly, the gen-set controller monitors an output voltage and current of the gen-set during a second period of time and uses them to calculate a second average power output of the gen-set. The gen-set controller then compares the first and second average power outputs to determine whether they differ by at least a predetermined amount. If the first and second average power outputs differ by at least the predetermined amount, the gen-set controller provides a control signal to cause a position of a throttle of the gen-set to change.
Although the gen-set controller of the '929 patent may adequately control operation of a gen-set to respond to relatively quick and/or large increases in load, its efficiency may be limited. Because the gen-set controller may not provide a control signal until after monitoring the power output of the gen-set for two periods of time, the response time of the engine to changing load demands may suffer and may even cause the engine to stall. For example, because incoming load increases may not be anticipated by the gen-set controller of the '929 patent until after two periods of time, the controller must adapt the gen-set to a drastic load change after the fact, thus creating a delay (i.e. temporary power shortage) in the output of the gen-set. Further, because the gen-set controller does not include a strategy for handling a load spike, it may drive the engine and alternator to suddenly produce a maximum power output during an overload period, thus risking engine stalling or lugging.
The present disclosure is aimed at overcoming some or all of the disadvantages associated with the prior art.